1. Field of the Invention
The present invention relates to an image signal recording apparatus, and more particularly, it relates to control of an operation performed at the time of starting/stopping recording.
2. Description of the Related Art
As an image recording/reproducing apparatus for recording a moving image, and reproducing the recorded image, there has conventionally been available a digital video tape recorder (VTR), which is designed to convert an image signal into a digital signal, and then record it on a magnetic tape. In this digital VTR, since a medium for recording is the magnetic tape, a video image is recorded by a sequential recording system for sequentially recording video image takes (video image information which is continuous in time and obtained from a start of a photographing recording operation to its stop) in a photographing order. Now, this system is described by referring to FIG. 8.
FIG. 8 shows the conventional sequential recording method for the magnetic tape.
As indicated by a reference numeral 801 of FIG. 8, upon an operation 801A of a recording start of the digital VTR, recording of a take 1 are started. By an operation 801B of a recording stop, the recording of the take 1 is stopped. Subsequently, by an operation 801C of a recording start, recording of a take 2 after the take 1 is started. Then, by an operation 801D of a recording stop, the recording of the take 2 is stopped. Thereafter, similar recording start designation is made for a take 3, and the take 3 is recorded after the take 2.
In the case of reproducing the video image recorded by the sequential recording method, an order of takes to be reproduced is similar to that of recording, and thus it is difficult to search a desired scene and change the order.
On the other hand, an apparatus has been presented, which is designed to record a video signal or an audio signal on a magnetic disk or a magneto-optical disk, which is a random-access medium, or a solid memory such as a flush memory or an SRAM. In the apparatus for recording a video signal in the random-access memory, the video signal is recorded at random in a space area of the memory. This apparatus is now described by referring to FIG. 9.
FIG. 9 shows states of video signals of takes 1 and 2 recorded on the random-access medium.
As indicated by reference numerals 901 and 902 of FIG. 9, take recording is started by each of operations 901A and 902A of recording starts, and the take recording is stopped by each of operations 901B and 902B of recording stops. The takes 1 and 2 are recorded in positions independent of each other on the medium. By this system, because of a medium characteristic, an order of reading-out is not dependent on an order of recording, enabling reading-out to be made optionally from any recoding area. Thus, it is possible to easily search and reproduce a preferred moving image directly, and change an order of a plurality of scenes.
In such a recording apparatus, by compressing an input digital signal to reduce the quantity of information, a great deal of moving image information or still image information can be recorded with a small storage capacity. There are various methods available for such a compression system of the image recording/reproducing apparatus.
For example, in the case of an orthogonal transformation method, an image is divided into blocks each composed of vertical n pixels and horizontal n pixels. Then, the image is quantized by performing orthogonal transformation such as discrete cosine transformation on each block, and rounding each obtained coefficient to a specified number of bits. Since image information is generally biased in a low-frequency area, the quantity of data can be reduced by reducing the number of bits of high-frequency components. In addition, in the case of a variable length coding method such as Huffman coding, efficient data compression can be performed by allocating shorter codes to a bit sequence having a higher appearance probability.
In the case of compressing a moving image, the quantity of data is greatly reduced by utilizing a characteristic of a strong correlation between image frames of the moving image so as to extract a difference between the frames.
In the moving image recording system, the quantity of data is reduced by combining such various compression techniques to compress the moving image, and then the image is recorded on the tape which is a sequential access medium, or the solid magnetic disk memory or the optical disk memory which is a random access memory.
In the foregoing recording apparatus, a scene changing effect such as cross fade has conventionally been applied to a joining part between the takes.
In the digital VTR using the sequential access medium, a scene changing effect such as cross fade must be applied during recording, and now this process is described by referring to FIG. 8.
As indicated by a reference numeral 802 of FIG. 8, when an effect such as cross face is applied to record an image signal, recording of the take 1 is started by a recording start operation 802A. When the recording of the take 2 is stopped by a recording stop operation 802B, one frame of a last scene of the take 1 is stored as a still image in an internal memory. Then, the still image stored in the memory is repeatedly read out according to a recording start operation 802C of the take 2. Cross fade processing is carried out such that a video image of a head part of the take 2 can appear little by little, and simultaneously the still image of the last scene of the take 1 can disappear little by little. Lastly, only a moving image of the take 2 remains. Then, the recording of the take 2 is stopped by a recording stop operation 802D.
In this case, because of a characteristic of the sequential access medium, data of the takes 1 and 2 cannot be read out simultaneously, or the data of the take 2 cannot be recorded while the data of the take 1 is read out. Consequently, as long as the respective takes are continuously recorded on one tape, cross fade from one moving image to another is impossible, and only cross fade from the still image to the moving image can be realized. Also, since a cross fade processing must be done during recording, a manipulation for executing cross fade processing must be performed during photographing, thereby complicating the manipulation operation. Consequently, a user cannot concentrate on photographing.
On the other hand, in the case of applying a scene changing effect such as cross fade to the data recorded on the random access medium, the foregoing drawbacks in the case of using the sequential access medium are solved. Hereinafter, description is made of the case of applying the scene changing effect such as cross fade to the joining part between the takes 1 and 2 recorded on the random access medium.
In the case of the random access medium, a scene changing effect such as cross fade can be applied not during recording but during reproducing. This process is now described by referring to FIG. 9.
In this case, as indicated by a reference numeral 903 of FIG. 9, the photographed take 1 is reproduced by a reproducing start operation 903A, and continued until an operation 903B. Then, reproducing of the take 2 is started at a point of time when the last part 903B of the take 1 to be subjected to cross fade is reproduced, and cross fade processing is executed from 903B to 903C such that a head part of the take 2 can appear little by little at the same time when a video after 903B of the take 1 disappears little by little. After 903C, only the video image of the take 2 is reproduced.
In the case of using the random access medium enabling the data of the takes 1 and 2 to be simultaneously reproduced, such cross fade processing can be executed during reproducing. In a cross fade part, by changing a mixing ratio of the two video images little by little, cross fade from one moving image to another can be realized.
Generally, the video image of the take is obtained by intentionally starting recording based on the recording start operation by the user, and intentionally stopping the recording based on the recording stop operation by the user. Thus, there is a high possibility that important video images are included throughout the takes.
Therefore, as described above, when a scene changing effect such as cross fade is applied between two moving image data by using the random access medium during reproducing, if an important video image is included in a last part of a first half moving image data (e.g., take 1) or a second half moving image data (e.g., take 2), such the important video image becomes unsharp because of fade-out or fade-in, and thus it cannot be seen clearly.